Quantum-confinement effect in individual Ge1- xSnx quantum dots on Si(111) substrates covered with ultrathin SiO2 films using scanning tunneling spectroscopy

The authors observed a quantum-confinement effect in individual Ge1−xSnx quantum dots (QDs) on Si (111) substrates covered with ultrathin SiO2 films using scanning tunneling spectroscopy at room temperature. The quantum-confinement effect was featured by an increase in the energy band gap of ∼1.5eV with a decrease in QD diameter from 35to4nm. The peaks for quantum levels of QDs became broader with a decrease in the height-diameter aspect ratio of QDs, demonstrating the gradual emergence of two dimensionality in density of states of quasi zero-dimensional QDs with the QD flattening.

[1]  Stefan Zollner,et al.  Optical critical points of thin-film Ge 1-y Sn y alloys: A comparative Ge 1-y Sn y /Ge 1-x Si x study , 2006 .

[2]  Y. Nakayama,et al.  Quantum regulation of Ge nanodot state by controlling barrier of the interface layer , 2006 .

[3]  H. Radamson,et al.  Low-temperature growth and critical epitaxial thicknesses of fully strained metastable Ge1−xSnx (x≲0.26) alloys on Ge(001)2×1 , 1998 .

[4]  A. G. Rodríguez,et al.  Determination of the optical energy gap of Ge1−xSnx alloys with 0 , 2004 .

[5]  Harry A. Atwater,et al.  INTERBAND TRANSITIONS IN SNXGE1-X ALLOYS , 1997 .

[6]  N. Tanaka,et al.  Observation of the quantum-confinement effect in individual β-FeSi2 nanoislands epitaxially grown on Si (111) surfaces using scanning tunneling spectroscopy , 2006 .

[7]  C. Bostedt,et al.  Strong quantum-confinement effects in the conduction band of germanium nanocrystals , 2004 .

[8]  B. Grandidier.  Scanning tunnelling spectroscopy of low-dimensional semiconductor systems , 2004 .

[9]  Boland,et al.  Evidence of pairing and its role in the recombinative desorption of hydrogen from the Si(100)-2 x 1 surface. , 1991, Physical review letters.

[10]  H. Atwater,et al.  Measurement of the direct energy gap of coherently strained SnxGe1–x/Ge(001) heterostructures , 2000 .

[11]  Alfonso Baldereschi,et al.  Band structure and instability of Ge1−xSnx alloys , 1989 .

[12]  A. G. Rodríguez,et al.  Ge1-xSnx alloys pseudomorphically grown on Ge(001) , 2003 .

[13]  M. Ichikawa,et al.  High-density ultrasmall epitaxial Ge islands on Si(111) surfaces with aSiO2coverage , 2000 .

[14]  Kentaroh Watanabe,et al.  Observation of the quantum-confinement effect in individual Ge nanocrystals on oxidized Si substrates using scanning tunneling spectroscopy , 2005 .

[15]  Kentaroh Watanabe,et al.  Quantum fluctuation of tunneling current in individual Ge quantum dots induced by a single-electron transfer , 2007 .

[16]  Christophe Delerue,et al.  Quantum confinement in germanium nanocrystals , 2000 .